This invention relates to improvements in low-profile inline filters, for use in intravenous (IV) sets and the like.
Low-profile inline IV filters are known in the art. They, like other IV filters, are generally connected in series with two portions of an IV tube to filter the fluid flowing through the tube. Low-profile inline filters offer an advantage over large, bulky filters in that they can be conveniently located on an IV line at a site close to the injection at which the IV line connects to a body, without causing an obstruction to the manipulation of the IV line and the injection needle, and without presenting a bulky mass that can disturb the IV connection either by pulling on it with its own weight or by being bumped, pulled, or snagged. Often a low-profile filter positioned close to the injection also provides a convenient hand grip for manipulating the IV line and the injection needle.
However, the known low-profile inline filters are generally assembled from a multiplicity of elements or units. The proliferation of elements has numerous disadvantages. The assembly of the filters becomes more complicated and time consuming with an increase in the number of elements. A proliferation of elements increases the chance for error during assembly, and thus it creates filter reliability problems. Because great care must be taken that the filters have no leaks, external or internal, at the points of connection of the various elements, the tolerances of the mating portions of the various elements must be kept close: an increase in the number of elements increases the number of portions at which close tolerances must be kept, thus increasing the manufacturing costs. And because the connections between elements are possible sources of leaks, an increase in the number of connections decreases filter reliability. Thus it can be seen that proliferation of the number of elements of which a filter is assembled increases the difficulty and cost of manufacture of the filters and may lead to decreased reliability, or a higher reject rate, of the assembled filters.
Furthermore, the known filters are generally constructed such that the mechanical strength of the filter is provided merely by the external filter housing, with the filtering element and its supporting structure being suspended within the filter housing. The mechanical strength of the filtering element support structure is thus not utilized to add to the mechanical strength of the filter. But in the case of inline filters, which, as was mentioned above, are often used as grips for manipulating the IV set, the stresses on the filter resulting from such manipulation may be so large that the filter housing alone may not be able to withstand them. Thus damage to the filters, such as fracture, may possibly result. Alternatively, reinforcing the structure of the filters may increase their manufacturing cost.